Techniques are being developed for the determination of isotopic abundances of C, H, N, and O in organic compounds. Required sample sizes are approximately one micromole for C, 10 micromoles for H. Precision is at the level of natural variations of isotope ratio). Multiple-collector mass spectrometers are being used, and the analytical developments include preparation procedures for H2, N2, CO and Co2 as the sample gases for H, N, O, and C, respectively.